1. Field of the Invention
The present invention relates to a cooling system for an engine. An engine body includes a cylinder bore, a water jacket, and a thermostat for controlling the flow of cooling water through the water jacket and a radiator in accordance with the temperature of the cooling water.
2. Background of the Invention
The above type of cooling system has been known from Japanese Patent Laid-Open No. Hei 11-82019. In the foregoing related art, the housing of the thermostat is supported between the cylinder head and the intake manifold. Furthermore, a wax case is supported by the housing in order to be slidable in a direction substantially orthogonal to the axis of the cylinder bore.
The thermostat projects extensively sideward from the engine body, which tends to reduce the layout tolerance of the cooling system. Furthermore, wax in contact with the cooling water expands or contracts depending upon temperature variations of the cooling water. As a result, the thermostat is subject to hunting if the cooling water temperature varies abruptly during warming-up of the engine. This can adversely affect the cooling performance for the engine body.
The invention has been made in order to overcome the foregoing problems of the background art, and provides an engine cooling system in which a thermostat projects from an engine body to a reduced extent and is protected against hunting in spite of abrupt variations in the cooling water temperature.
In accordance with a first feature of the present invention, there is provided a cooling system for an engine comprising an engine body having a cylinder bore and a water jacket, and a thermostat for controlling the passage of cooling water between the water jacket and a radiator in accordance with the temperature of the cooling water. In the cooling system, the thermostat includes a cylindrical housing with a sliding space and an inlet and an outlet which open onto an inner surface of the sliding space and face each other. Furthermore, a wax case which houses wax therein is slidable between positions for enabling and disabling communication between the inlet and the outlet in response to expansion or contraction of the wax. The wax case is slidably fitted in the sliding space. The housing, in which an axis of the sliding space is parallel to an axis of the cylinder bore, is directly attached to the engine body.
With the foregoing configuration, the thermostat is attached to the engine body such that the wax case slides in a direction parallel to the axis of the cylinder bore. This is effective in reducing a projecting amount of the thermostat from the engine body, and improving layout tolerance of the cooling system by assembling the thermostat in the engine body in a compact state. Furthermore, heat is transferred from the engine body to the wax, which is housed in the wax case, via the wax case and the housing. Therefore, even when cooling water temperature changes abruptly, a temperature of the wax exactly corresponds to a temperature of the engine body. This protects the thermostat against hunting, and improves the cooling performance. Furthermore, the path for circulating the cooling water in the thermostat can be simplified, and a resistance in the path can be reduced.
According to a second feature of the present invention, the housing is sandwiched between a cylinder block and a cylinder head that constitute a part of the engine body and are coupled with each other. No additional component is required in order to attach the thermostat to the engine body. In other words, the thermostat can be attached to the engine body using a reduced number of components.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.